Please help...

Where can I find more information about this pair...

Is that true that the parasitic climbes onto the fish head during the night when the fish sleeps upside down?

Thx

Hi Darek

a very nice photo of a parasitic isopod, sometimes improperly called "fish louse" (the true fish louse is a different crustacean)

maybe it's Anilocra sp., Anilocra is the most common genus of the family Cymothoidae on European coasts, the IWP genera may be idfferent

I have seen photos of these isopods in a fish's mouth (e.g., on the base of the tongue), I don't really know how they get there, I suspect either through the gill slits or through the mouth, during larval or early post-larval stage .. the isopod has very strong hooked dactyli (simple claws), so it can have a very solid grip and avoid to be swallowed by the fish ..

cheers

Art

I agree with everything Art said, and, by the way, fish don't sleep upside down, they just stop swiming and take a rest at night, or at least some of them do. The one in your photo (a soldierfish, genus Myripristis) is a nocturnal fish; it feeds mostly on plankton at night and rests in the reef during the day.

Luiz

I remember I've seen a short story ilustrating this case. The fish was upside down and the parasitic isopod was climbing its head. Or I had a dream

It's a very good and interesting photo. I saw something similar last wednesday in a night dive:

Is it the same isopod? I have seen them in many different kinds of fishes, on the mouth, head, tail and fins.

I was asked to prepare material about this pair for National Geogrpahic so I did my research and I did see this fish upside down...

http://www.fishbase.org/Summary/SpeciesSum...iesname=jacobus

Found from shallow coral reefs to offshore deeper waters (Ref. 3724). A nocturnal species aggregating around coral reefs and deeper rocky reefs (Ref. 3724). Feeds mainly on planktonic organisms (Ref. 3724). Occasionally found swimming upside down (Ref. 9710). Marketed fresh but not popular as a food fish (Ref. 5217).

There you go...

I never said they don't swim upside down, what I said was that they don't sleep Several fish that live in caves (lionfish, royal basslet, many blennies, etc.) swim oriented to the wall of the cave. When the wall becomes a roof they swim upside down.

Luiz